Aqueous latex copolymer compositions

Abstract

Aqueous latex compositions for use as contact adhesives comprising a mixture of an amorphous copolymer A and an amorphous copolymer B and preferably a tackifying resin where A comprises units of vinylidene chloride, an internally plasticizing comonomer like 2-ethylhexyl acrylate or n-butyl acrylate, and optionally a copolymerizable acid, and has Tg in the range -50° to <0° C. and B comprises units of vinylidene chloride, an alkyl acrylate and/or methacrylate or certain other comonomers, and optionally a copolymerizable acid, and has a Tg in the range 0° to 80° C., and wherein copolymer A has a modal molecular weight Mp within the range 100,000 to 700,000.

We claim: 
     
       1. An aqueous latex composition comprising at least one copolymer A and at least one copolymer B, wherein: A is an amorphous copolymer comprising 10 to 70 weight % of polymerised units of vinylidene chloride, 30 to 90 weight % of polymerised units of said at least one internally plasticising comonomer, 0 to 20 weight % of polymerised units of vinyl chloride, and 0 to 10 weight % of polymerised units of at least one copolymerisable ethylenically unsaturated acid and which copolymer A has a Tg in the range -50° to <0° C.; and   B is an amorphous copolymer comprising 10 to 70 weight % of polymerised units of vinylidene chloride; 2 to 90 weight % of polymerised units of at least one comonomer selected from alkyl acrylates and methacrylates having 1 to 12 carbon atoms in the alkyl group, alkoxyalkyl acrylates and methacrylates having 1 to 12 carbon atoms in the alkyl groups, styrene, acrylonitrile, vinyl acetate and vinyl ethyl ether; 0 to 50 weight % of polymerised units of vinyl chloride; and 0 to 10 weight % of polymerised units of at least one ethylenically unsaturated acid; and which copolymer B has a Tg in the range from 0° to 80° C.   and wherein the dry weight ratio of the at least one copolymer A: the at least one copolymer B is from 95:5 to 10:90;   and wherein said at least one copolymer A has a modal molecular weight Mp (as herein defined) within the range 100,000 to 700,000;   and wherein said composition provides contactable layers after drying.   
     
     
       2. An aqueous latex composition according to claim 1 wherein said at least on copolymer A comprises polymerised units of at least one copolymerisable ethylenically unsaturated acid. 
     
     
       3. An aqueous latex composition according to claim 2 wherein said at least one copolymer B comprises polymerised units of at least one copolymerisable unsaturated acid 
     
     
       4. An aqueous latex composition according to claim 1 wherein the weight ratio of said at least one copolymer A: said at least one copolymer B is from 85:15 to 15:85. 
     
     
       5. An aqueous latex composition according to claim 1 wherein the Tg of said at least one copolymer A is in the range from -40° to -5° C. 
     
     
       6. An aqueous latex composition according to claim 1 wherein the proportion of polymerised units of vinylidene chloride units in copolymer A is 20 to 60 weight %. 
     
     
       7. An aqueous latex composition according to claim 6 wherein the proportion of polymerised units of said at least one internally plasticising comonomer in copolymer A is 40 to 80 weight %. 
     
     
       8. An aqueous latex composition according to claim 7 wherein the proportion of polymerised units of said at least one ethylenically unsaturated acid is 0.1 to 8 weight %. 
     
     
       9. An aqueous latex composition according to claim 1 wherein the at least one internally plasticising comonomer is selected from n-butyl acrylate and 2-ethylhexyl acrylate. 
     
     
       10. An aqueous latex composition according to claim 1 wherein the Mp of said at least one copolymer A is in the range of from 100,000 to 500,000. 
     
     
       11. An aqueous latex composition according to claim 1 wherein the Tg of said at least one copolymer B is in the range of from 2° to 60° C. 
     
     
       12. An aqueous latex composition according to claim 1 wherein the proportion of polymerised units of vinylidene chloride in said at least one copolymer B is 35 to 70 weight %. 
     
     
       13. An aqueous latex composition according to claim 12 wherein the proportion of polymerised units of said at least one comonomer selected from alkyl acrylates and methacrylates having 1 to 12 carbon atoms in the alkyl groups, alkoxyalkyl acrylates and methacrylates have 1 to 12 carbon atoms in the alkyl groups, styrene, acrylonitrile, vinyl acetate, and vinyl ethyl ether, is 5 to 90 weight %. 
     
     
       14. An aqueous latex composition according to claim 13 wherein the proportion of polymerised units of said at least one ethylenically unsaturated acid is 0.1 to 8 weight %. 
     
     
       15. An aqueous latex composition according to claim 1 wherein said at least one copolymer B includes polymerised units of at least one internally plasticising comonomer. 
     
     
       16. An aqueous latex composition according to claim 1 wherein said at least one copolymer B includes units of at least one comonomer within the scope of alkyl acrylates and methacrylates having 1 to 12 carbon atoms in the alkyl group and alkoxyalkyl acrylates and methacrylates having 1 to 12 carbon atoms in the alkyl group which comonomer is not an internally plasticising comonomer. 
     
     
       17. An aqueous latex composition according to claim 1 wherein the at least one comonomer providing polymerised units in copolymer B selected from alkyl acrylates and methacrylates having 1 to 12 carbon atoms in the alkyl group, alkoxyalkyl acrylates and methacrylates having 1 to 12 carbon atoms in the alkyl groups, styrene, acrylonitrile, vinyl acetate, and vinyl ethyl ether, is at least one alkyl acrylate or methacrylate having 1 to 12 carbon atoms in the alkyl group. 
     
     
       18. An aqueous latex composition according to claim 1 wherein said at least one comonomer providing polymerised units in copolymer B selected from alkyl acrylates and methacrylates having 1 to 12 carbon atoms in the alkyl group is at least one of methyl methacrylate, n-butyl acrylate and 2-ethylhexyl acrylate. 
     
     
       19. An aqueous latex composition according to claim 18 wherein said at least one comonomer in copolymer B is methyl methacrylate together with n-butyl acrylate. 
     
     
       20. An aqueous latex composition according to claim 1 wherein copolymer A and/or copolymer B comprise polymerised units of at least one copolymerisable ethylenically unsaturated acid selected from an ethylenically unsaturated carboxylic acid or sulphonic acid. 
     
     
       21. An aqueous latex composition according to claim 20 wherein said acid is an aliphatic alpha, beta unsaturated carboxylic acid. 
     
     
       22. An aqueous latex composition according to claim 1 wherein said copolymer A and/or copolymer B comprise polymerised units of at least one type of comonomer to provide a cross-linking functionality. 
     
     
       23. An aqueous latex composition according to claim 1 wherein said composition includes at least one tackifying resin. 
     
     
       24. An aqueous latex composition according to claim 1 wherein said copolymer A has been formed by a monomer-flooded polymerisation process. 
     
     
       25. A process of contact bonding which comprises coating two substrates to be bonded with an aqueous latex composition according to claim 1; allowing the aqueous-based coating on each substrate to dry; and bringing the dry coated substrate into contact to affect contact bonding.